[qiāo zhū gàng]   

敲    竹    杠    比喻利用别人的弱点或以某种口实为借口来索取财物。 贬义>

指利用他人的弱点或找借口来索取财物或抬高价格，比喻利用别人的弱点或以某事为借口来讹诈。

Take advantage of sb.'s being in a weak position to overcharge him

敲金击玉    敲牛宰马    敲冰玉屑    敲金戛玉    敲锣放炮